1. Field of the Invention
The present invention relates to a steam turbine power plant provided with a high-temperature steam turbine, and more particularly to a steam turbine power plant provided with a steam turbine which has individual configuration portions formed of a suitable heat-resisting alloy, a heat-resisting steel or the like.
2. Description of the Related Art
Energy saving of the thermal power system is being performed vigorously after the energy crisis, generation of CO2 is being suppressed and needs for high efficiency are increasing in view of the global environmental protection in these years.
The conventional steam turbine power generation systems have a steam temperature of up to approximately 600° C., so that a ferrite-based heat-resisting steel is used for the main members such as a turbine rotor, a casing and the like of the steam turbine. In order to achieve the above-described energy saving and high efficiency, it is most effective for the steam turbine system to raise the steam temperature of the steam turbine to a high level to increase power generation efficiency.
But, in a case where the power generation efficiency is improved by raising the steam temperature of the steam turbine to, for example, 650° C. or more, it is hard to apply the structure of a conventional steam turbine power generation system as it is in view of the mechanical characteristics and environment resistance because the conventional steam turbine power generation system uses a ferrite-based heat-resisting steel for the main members such as a nozzle, a turbine rotor, a casing and the like of the steam turbine.
Under the circumstances described above, it is being studied to use an Ni base alloy, an austenite-based material or the like as a material of the turbine portions which are exposed to high-temperature steam in these years. The Ni base alloy and the austenite-based material are poor in workability, productivity and economical efficiency in comparison with the ferrite-based material. To use these materials for the turbine portions, various kinds of efforts have been made as disclosed in, for example, Japanese Patent Laid-Open Application No. Hei 4-171202, Japanese Patent No. 3095745, Japanese Patent No. 3582848, and Japanese Patent Laid-Open Applications No. 2000-274208, No. 2000-282805, No. 2000-282807, No. 2000-282808and No. 2004-169562. Among these disclosed technologies, it is being studied to use the turbine casing and the turbine rotor in a state divided into a high-temperature portion and a low-temperature portion in these years as disclosed in, for example, Japanese Patent Laid-Open Applications No. 2000-274208 and No. 2000-282808.
But, where the Ni base alloy or the austenite-based material is used to realize a highly efficient steam turbine power generation system, there are still problems that they are poor in economical efficiency in comparison with the ferrite-based material and also poor in productivity of a large steel ingot as described above.